Why does Lenz's law have a minus sign?

The minus sign shows that the direction of induced current always opposes the change that created it. So when certain metals are cropped through say a copper tube they slow down. Show video of Lenz's law in action. The current is induced in the opposite direction to ensure that energy is conserved and not created from nothing.
When pushing a magnet into a coil, if you push the North pole towards the coil first then a North pole is induced in the coil to repel the magnet. The magnet is slowed down and repelled by the coil, the kinetic energy here is dissipated as heat.